Among all industrialized countries, the United States has the highest rate of sexually transmitted infections (STIs) in adolescents and of unintended teenage pregnancy. Only one randomized behavioral intervention trial, Project Respect, has shown a significant impact on reduction of STI incidence in adolescents. Unfortunately, practitioners and clinics have not widely adopted this intervention, which is perceived as too resource-intensive. Improved prevention and control of STI/HIV infection, especially in adolescents, requires innovative and sustainable clinical and public health approaches. The objective of this career development award is to gain expertise in research methodologies for behavioral interventions targeting adolescents, with a long-term research goal of reducing STI/HIV infection and unintended pregnancy in adolescents and young adults. This application proposes development and pilot evaluation of a preventive intervention for adolescents engaging in high-risk sexual behaviors;and outlines the educational objectives needed to strengthen my background and skills in behavioral intervention research, including advanced training in behavioral research theory and application;qualitative research design;intervention study design and assessment - specifically including brief clinician-delivered interventions;the use of innovative biomarker outcomes in behavioral intervention trials;and cost-effectiveness analysis - all in relationship to adolescent sexual health and behaviors. The proposed intervention is a clinician-delivered brief intervention for adolescents engaging in high-risk sexual behaviors - easily adopted by medical providers, and sustainable in clinic settings. The specific aims of this proposal are to: 1) develop a brief clinician-delivered client-centered intervention for 14-19 year olds engaging in high-risk sexual behaviors and assess the feasibility, acceptability, and cost of the intervention in adolescents attending an STD Clinic;2) conduct a pilot study to assess the impact of this intervention on subsequent sexual risk behaviors in adolescent STD clinic patients;and 3) develop a proposal for a randomized controlled trial designed to definitively test the efficacy of this STD clinic-based intervention in reducing incidence of STI and unintended pregnancy;to assess the cost- effectiveness of the intervention;and to further explore the feasibility of extending the intervention to other clinical settings that serve adolescents.